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MASTER PLANNING AND TREATMENT PROCESS SELECTION 2. ] 5

less common or special contaminants such as those that may be found in the USEPA list-
ing of inorganic, synthetic, and volatile organic contaminants. Where these exist, special
treatment accommodation may be required. It is possible, however, that existing treatment
for more common contaminants may be effective in reducing the amount of special con-
taminant or at the least provide necessary pretreatment. In very general terms, treatment
methods that may be considered for contaminants in the three categories mentioned above
are as follows:
• lnorganics. Oxidation or chemical reaction to produce innocuous compounds or pre-
cipitates and/or ion-exchange following filtration.
• Synthetic organics. Herbicides and pesticides, most of which may be removed in GAC
columns. Some contaminants may be preconditioned by strong oxidants.
• Volatile organics. Removed by air stripping and/or in GAC columns.
There are a number of special or infrequently found contaminants that have not been
discussed. Wherever special or less common contaminants may exist in source waters, it
is always essential that detailed investigations, possibly including pilot studies, be con-
ducted before treatment facilities are designed.

Treatment Comparisons and Evaluations
While the treatment rules become more demanding, the list of available "tools of the trade"
is also expanding. It is up to the designer to take advantage of the many treatment re-
sources discussed later in this text that are best adapted to the particular plant application.
The principal intent of these discussions is to emphasize that many treatment options
and combinations of options are available to the designer and that all viable options must
be investigated to achieve that treatment or combination of treatments best suited for the
particular application. It is also essential that issues other than treatment capability be in-
vestigated for each option and each treatment train. These other issues may include the
following (not necessarily in order of importance):
• Construction cost
• Annual operation costs
• Site area required
• Complexity of operation (required capability of operating staff and laboratory moni-
toring)
• Operation risk (most common causes, if any, of treatment failure)
• Flexibility of plant arrangement for future changes
• Waste disposal options

Consideration of viable options would also be critical to provide a flexible facility
arrangement in which additions and modifications may be made for future treatment re-
quirements. Drinking water treatment design is not static; it is a dynamic, ever-changing
process.